LED control devices for controlling the brightness of two (a plurality of) LED devices have been known (for example, see JP 2015-041588 A).
Such conventional LED control devices include, for example, a smoothing circuit that outputs a reference signal obtained by smoothing a PWM light controlling signal, and a control unit that controls a plurality of switching elements for controlling an LED current flowing through each of the LED device based on the reference signal.
The control unit uses a voltage detected by a detection resistor, through which the current flowing through each switching element also flows, to control the LED current flowing through each of the two LED devices to have a value according to the reference signal.
If the two PWM light controlling signals have substantially the same frequency and duty ratio, the operational frequencies of the two switching elements controlled based on the PWM light controlling signals may be synchronized.
The synchronized operational frequencies of the two switching elements affect the detection of the voltage at each switching element. This causes a problem in that the control unit may fail to control each switching element in a desired manner, and thus fail to supply a predefined LED current to the two LED devices.